The present invention relates to a system for treating bilge water that has been contaminated by wastewater generated by ship-board fire-fighting operations.
Various types of contaminants are found in the ballast and bilge water of ships as the result of routine on-board ship operations including, but not limited to, equipment and deck cleaning, laundry cleaning, food preparation and the use of on-board showers and sinks. These routine operations cause contamination of the bilge water with various size particles of dirt and rock, oil and detergents. Detergents typically include a combination of organic compounds, volatile organic compounds and halogens. In addition to the foregoing routine activities, fires and associated fire-fighting activities occasionally occur on-board requiring the use of firehoses through which are ejected high volumes of water that drains into the ship bilges. Water used to suppress fires washes significant volumes of the combustibles (upon which it is sprayed to put the fire out) down to the bilge, including petrochemical fuels, paint residues and any of the various cargo or byproducts of their combustion that may be carried on ships. In addition, firefighting water frequently is augmented with foaming fire suppressant chemical compositions, such as aqueous film-forming foams (xe2x80x9cAFFFxe2x80x9d). AFFF is a well-known, water soluble mixture of fluorochemical surfactants, hydrocarbon surfactants and solvents. AFFF is often provided in a 3% solution with water specifically for use in fighting fires in many environments, including on board ships.
Accordingly, routine ship-board operations, as well as accidents, spills and fire-fighting activities, result in the presence of an almost unlimited variety of chemical contaminants to be present in bilge water, including benzene, toluene, ethylene, xylene, oil, grease, chloroform, nitrates, nitrogen, lead, zinc, cadmium, tin, mercury, nickel, copper, arsenic, selenium, chromium, diethylene glycol butyl ether, sodium nitrate, triethanolamine, and 1H-benzotriazole. The discharge of wastewater containing the foregoing contaminants into the ocean, or into land-based treatment facilities, is strictly regulated by federal and state governmental agencies, as well as by foreign countries and the international community. Accordingly, there has been a need for processes and systems that remove such contaminants from shipboard wastewater and which are compact and lightweight enough to be operated on-board ships.
As the result of the above-described circumstances, various on-board wastewater treatment systems have been developed, some of which tend to focus on certain categories of contaminants. For example, the bilge water treatment system that is disclosed in U.S. Pat. No. 4,066,545 focuses on the separation of oil from bilge water. U.S. Pat. No. 5,498,346 discloses a system that utilizes cyclones to physically separate oil from wastewater during oil spill cleanup operations.
The ship-board system disclosed by U.S. Pat. No. 4,846,976 focuses on the removal of oil, grease, and insoluble solids from contaminated bilge and wastewater and discloses a filtration system suitable for use on small ships to treat wastewater containing an emulsion of water, oil or fat, an emulsifying agent and insoluble solid material. While the disclosure of U.S. Pat. No. 4,846,976 mentions that detergents are introduced into ship ballast tanks and bilges from fire foams and other sources, the purpose of the filtration system disclosed in U.S. Pat. No. 4,846,976 is to remove only the insoluble solids and the oil, leaving the detergents and firefighting foam contaminants in the wastewater. In addition, it can be noted that since the date of issue of U.S. Pat. No. 4,846,976, wastewater discharge regulations have become more stringent, resulting in a need for a process that can also remove the detergent chemicals, as well as a greater portion of the solids, oils and other contaminants.
U.S. Pat. No. 4,071,445, on the other hand, discloses a system that is designed to treat on-board wastewater that is contaminated with sewage-type waste (i.e, xe2x80x9cblack waterxe2x80x9d), as well as by wastewater from showers, kitchen facilities, etc. (i.e., xe2x80x9cgrey waterxe2x80x9d). U.S. Pat. No. 4,071,445 is directed to installations on small ships that are primarily focused on reducing biological oxygen demand (BOD), suspended solids (SS), coliform bacteria, as well as other debris and larger solids.
Similarly, the method and apparatus disclosed in U.S. Pat. No. 5,254,253 are designed to remove biological contaminants, in addition to oil and grease, from shipboard waste or bilge water. The method of U.S. Pat. No. 5,254,253 combines on-board black water (raw sewage), grey water (wastewater from showers, kitchen facilities, etc.) and bilge water (containing oil and grease) in an aerated, on-board membrane-bioreactor system where microbes digest the various biological, organic and oily contaminants.
In contrast to the above-described bioreactor system, U.S. Pat. No. 5,932,112 discloses an on-board method and apparatus to kill unwanted aerobic and anaerobic microbes in bilge water by alternately removing and introducing oxygen into the wastewater.
U.S. Pat. No. 5,139,679 discloses a method to decontaminate bilge water that is contaminated with citric acid, triethanolamine and heavy metals. Such contamination occurs when cleaning agents, commonly consisting of solutions of citric acid and triethanolamine, are used to remove old paint and rust from bilges. More specifically, the method of U.S. Pat. No. 5,139,679 treats such contaminated bilge water with hydrogen peroxide and ultraviolet light in the presence of a ferrous ion catalyst, which results in the destruction and decomposition of citric acid and triethanolamine. The chemical decomposition of citric acid and triethanolamine, in turn, prevents the heavy metal contaminants from forming chelated compounds, thereby permitting their subsequent removal by conventional precipitation methods involving pH-adjusting methods.
Notwithstanding the development of the foregoing on-board wastewater treatment systems, there remains a need for a bilge water treatment system that can more effectively remove or reduce a greater variety of contaminants from contaminated bilge water. For example, known bilge water treatment systems do not remove AFFF or its chemical constituents. Furthermore, the above-discussed wastewater treatment systems do not remove multiple categories of contaminants, i.e., solids, AFFF constituents, organic and volatile organic contaminants, solvents, oil and metals, but are more narrowly focused to treat or remove a more specific category of contaminants. In addition, the concentration and variety of contaminants that must be removed from wastewater, prior to legal discharge or disposal is significantly greater than it was just five or ten years ago, due to more stringent regulatory standards. Accordingly, there is a need for a comprehensive wastewater treatment system that removes, or reduces to acceptable levels, multiple categories of contaminants, but that is still highly portable and easily assembled for operation on board ships. As described hereinafter, the present invention addresses the foregoing shortcomings of the prior art.
The problems and disadvantages associated with known apparatus and methods for decontaminating water at a site of a reservoir holding contaminated water are solved by the apparatus of the present invention which includes a plurality of water processing modules, each having an independent support structure for holding at least one associated water processing device in an position suitable for transport to and operation at the site of the reservoir holding the contaminated water. The at least one associated water processing device of each of the plurality of modules is selectively and removeably hydraulically connectable to another of the associated water processing devices to define a continuous flow path extending from an inlet to the apparatus into which contaminated water flows, through said apparatus to an outlet from which decontaminated water is discharged. Each of the at least one associated water processing devices has an associated decontamination function for at least partially removing a contaminant from a flow of the contaminated water passed sequentially through the of modules along the flow path.
The method of the present invention for removing various contaminants from a volume of contaminated water contained in a reservoir, comprises the steps of providing a plurality of water processing modules, each having an independent support structure for holding at least one associated water processing device in a position that is suitable for transport to, and operation at, the site of the reservoir holding the contaminated water, the associated water processing device of each of the modules being selectively and removeably hydraulically connectable to another associated water processing device of another of the modules to define a continuous flow path extending from an inlet of the apparatus, into which contaminated water flows, through the apparatus, to an outlet from which decontaminated water is discharged, each of the associated water processing devices having an associated decontamination function for at least partially removing a contaminant from a flow of the contaminated water passed sequentially through the plurality of modules along the flow path; transporting the plurality of modules to a position proximate to the reservoir; placing the modules on a support surface in a selected relative juxtaposition; connecting the water processing devices to configure the flow path; operating the apparatus to remove contaminants from the contaminated water; disconnecting the water processing devices; and removing the modules from the site.